Cargo carriers, designed for clamping on a pair of crossbars mounted on top of a vehicle, continue to become more popular for increasing a vehicle's carrying capacity. External boxes provide a convenient compartment for carrying equipment or gear that may be desirably segregated from the main passenger compartment of the vehicle due to the shape or size of the cargo, or the fact that the cargo may be wet, dirty, etc. However, boxes present new challenges and problems to be addressed. For example, external boxes create extra drag creating noise and/or decreased efficiency (lower gas mileage). Boxes may make it difficult or impossible to safely drive in or under certain garages or parking structures due to their height above the vehicle. Boxes may also be difficult to access because of their location on top of a vehicle. It also may be difficult to view the interior of a cargo box due to its position or a lack of light. The box concepts described below may provide benefits and/or solutions to one or more of the problems mentioned above, among others.